A multitude of manufacturing processes use band-type workpieces, such as textile weaves or knits, synthetic-resin foils, paper, and the like. Frequently at least one longitudinal edge of such a workpiece rolls up or bends over, necessitating flattening out of the workpiece before it can be employed in the manufacturing process. In many processes where the workpiece is advanced longitudinally at high speed the nature of the transport for such a workpiece inherently causes the longitudinal edges to curl up. Furthermore the type of workpiece itself usually causes the bending over or rolling up to take place at one face of the workpiece rather than the other.
It has been suggested, as in German published specifications Nos. 1,460,650 and 2,218,916 as well as in German Pat. Nos. 250,987 and 462,889, to flatten these bent-over edges out by means of rods, disks or wheels, or by means of smoothing bands running transverse to the direction of transport of the workpiece having the bent-over edge. All such systems rely on the flattening tool physically engaging the workpiece and smoothing out the bent-over edge.
The principal disadvantage of this arrangement is that the flattening tool can damage the workpiece. This is especially the case for thin synthetic-resin foils.
Another disadvantage of these known flattening systems is that they are not readily adapted to fit into other manufacturing processes. Very often the goods must be slowed down considerably at the flattening location so that the entire process must be similarly slowed down in order to allow for the flattening procedure to be effective. Furthermore most known flattening arrangements cannot tolerate any variation in speed of the goods, as the lateral rolling-out must take place at a rate directly proportional to the displacement rate. Any slowing down or speeding up can cause the goods to be damaged or shifted sideways. Another disadvantage of the known systems is that the band whose edges are being flattened out must almost invariably be spanned relatively tightly longitudinally in a manner that is not necessarily acceptable for many types of workpieces.